In the semiconductor industry, the lens of an exposure apparatus is used to perform a magnification conversion to a pattern of a mask, thereby transferring the pattern onto a wafer. The resolution dimensions on the wafer are at least a micrometer or smaller; because the resolution dimension approaches the dimension of the diffraction limit, the optical quality is estimated by considering the wavefront error. In view of the wavefront, any deformation occurring on a lens surface can change the phase of a light wave, so that through the wavefront distortion of each lens, the light wave on the imaging surface can create a superposed final wavefront error. Therefore, a lens assembly including a large-diameter lens (having an outer diameter (φ>150 mm) can suffer the following situation: even if the lens is perfect and is located in a correct position, a good image-forming quality cannot be guaranteed. The reason for this situation is that the lens surface deformation and the stress, generated from the lens own-gravity and the lens clamping, cause the optical quality to decrease. When a firmly fixed mechanism of an annular support used for a common miniature lens is applied to the large-diameter lens, the deformation generated by the firmly fixed mechanism is too large; therefore, it is unsuitable to apply the firmly fixed mechanism to the large-diameter lens, and it is necessary to use an additional specific design.
A firmly fixed mechanism applied to the large-diameter lens basically follows the kinematic principle of the design concept: the freedoms of a rigid body include three translation freedoms and three rotation freedoms; in order to firmly fix an element, it is necessary to apply six linearly independent constraint forces; when an element is clamped in a situation of over constraint, the clamped element can still have inner stress and deformation; when the clamping condition meets a kinematic constraint condition, the deformation of the element can be minimized. However, the rigid contact of the kinematic principle is assumed to be a point contact. The point contact applied to the lens can result in a problem that the contact stress is too large, so that the contact point is enlarged to form a small-area contact; such a design is called a semi-kinematic design. In the prior art, many firmly fixed mechanisms applied to large-diameter lenses are designed according to this semi-kinematic principle.
U.S. Pat. No. 7,085,080 B2 discloses a low-deformation support device of an optical element. U.S. Pat. No. 6,594,093 B2 discloses an adjusting apparatus for an optical element in a lens system. U.S. Pat. No. 6,239,924 B1 discloses a kinematic lens mounting with distributed support and radial flexure. U.S. Pat. No. 6,400,516 B1 discloses a kinematic optical mounting. European Patent No. 0230277 B1 discloses a precision lens mounting. U.S. Pat. No. 8,654,461 B2 discloses a lens positioning unit of an optical system. U.S. Pat. No. 7,903,353 B2 discloses a laterally adjustable optical mount with bent lever manipulator units. China Patent No. 102279454 B discloses a support device of a lens in a photoetching projection objective.